Abstract: In some examples, a transmit assembly is described that may include a first optical transmitter, a second optical transmitter, and a polarizing beam combiner. The first optical transmitter may be configured to emit a first optical data signal centered at a first frequency. The second optical transmitter may be configured to emit a second optical data signal centered at a second frequency offset from the first frequency by a nominal offset n. The polarizing beam combiner may be configured to generate a dual carrier optical data signal by polarization interleaving the first optical data signal with the second optical data signal. An output of the polarizing beam combiner may be configured to be communicatively coupled via an optical transmission medium to a polarization-insensitive receive assembly.

Abstract: Thermal chirp compensation in a chirp managed laser. In one example embodiment, a laser package including a laser and an optical spectrum reshaper configured to convert frequency modulated optical signals from the laser into an amplitude modulated optical signals is provided. A thermal chirp compensation device is in communication with the laser package and a laser driver. The thermal chirp compensation device includes means for generating bias condition and temperature specific thermal chirp compensation signals that each corresponds to a predetermined level of thermal chirp that is induced in the laser by operating the laser at a particular bias condition and temperature.

Abstract: Thermal chirp compensation in a chirp managed laser. In one example embodiment, a laser package including a laser and an optical spectrum reshaper configured to convert frequency modulated optical signals from the laser into an amplitude modulated optical signals is provided. A thermal chirp compensation device is in communication with the laser package and a laser driver. The thermal chirp compensation device includes means for generating bias condition and temperature specific thermal chirp compensation signals that each corresponds to a predetermined level of thermal chirp that is induced in the laser by operating the laser at a particular bias condition and temperature.

Abstract: An wave division multiplexed (WDM) optical transmitter is disclosed including a directly modulated laser array and a planar lightwave chip (PLC) having a plurality of OSRs that receive outputs of the laser array and increase the extinction ratio of the received light. An optical multiplexer receives the outputs of the OSRs and couples them to a single output port. The multiplexer has transmission peaks through its ports each having a 0.5 dB bandwidth including the frequency of a laser in the array. The optical multiplexer may be embodied as cascaded Mach-Zehnder interferometers or ring resonators.

Abstract: Apparatus and methods for driving a transmitter to generate DNPSK signals is disclosed including generating N data streams comprising data symbols and for each of a plurality of sets of N simultaneous data symbols of the N data streams, imposing signals are on L of a plurality of signal lines, with the value of L corresponding to values of the N simultaneous data symbols. Signals on the plurality of signal lines are ANDed with a clock signal synchronized with the N data streams to produce RZ signals. The RZ signals are summed and the summed signal is input to a laser that produces an output having frequency modulation corresponding to the magnitude of the summed signal. The output of the laser is passed through an optical discriminator.

Abstract: Thermal chirp compensation in a chirp managed laser. In one example embodiment, a method for thermal chirp compensation in a chirp managed laser (CML) includes several acts. First, a first bias condition and temperature is selected. Next, a first thermal chirp compensation signal is generated. Then, the laser is driven by biasing a first input drive signal with the first thermal chirp compensation signal. Next, a second bias condition and temperature is selected. Then, a second thermal chirp compensation signal is generated. Finally, the laser is driven by biasing a second input drive signal with the second thermal chirp compensation signal.

Abstract: An optical transmitter is disclosed wherein a signal processor receives a data stream and outputs a drive signal for a laser, where the drive signal encodes each bit of the data stream according to the values of adjacent bits effective to compensate for spreading of bits within the fiber. The output of the laser is input to an optical spectrum reshaper that outputs a signal having an enhanced extinction ratio.

Abstract: An optical transmitter is disclosed wherein a modulating signal, such as an NRZ signal, encoding data is combined with a time derivative of the modulating signal and coupled to a directly modulated laser in order to generate artificial transient chirp in the output of the laser effective to substantially compensate for dispersion experienced by the output of the laser traveling through a dispersive medium such as an optical fiber. In some embodiments, the time derivative is added to the modulating signal only at the falling edges of the modulating signal.

Abstract: A high-speed optical transmitter comprises multiple digital lanes that are provided to a bank of digital-to-analog converters. The analog signals are then used to Phase Shift Keyed (PSK) modulation using a Chirp Managed Laser (CML)-based transmitter, and potentially using dual polarization. A corresponding optical receiver receives the sequence of optical signals at a demodulator. For each polarization, the demodulator includes a corresponding demodulation channel that is configured to demodulate that polarization component of the optical signal into one or more signal components. Each of these signal components is converted into a corresponding digital signal using a corresponding analog-to-digital converter. In the case of higher-order PSK modulation (e.g., 8PSK or higher), for each polarization, the analog converter has a lower sampling rate than for QPSK modulation.

Abstract: The frequency chirp modulation response of a directly modulated laser is described using a small signal model that depends on slow chirp amplitude s and slow chirp time constant ?s. The small signal model can be used to derive an inverse response for designing slow chirp compensation means. Slow chirp compensation means include electrical compensation, optical compensation, or both. Slow chirp electrical compensation can be implemented with an LR filter or other RF circuit coupled to a direct modulation source (e.g., a laser driver) and the directly modulated laser. Slow chirp optical compensation can be implemented with an optical spectrum reshaper having a rounded top and relatively large slope (e.g., 1.5-3 dB/GHz). The inverse response can be designed to under-compensate, to produce a flat response, or to over-compensate.

Abstract: A method for generating D-N-PSK optical signals is disclosed wherein a laser is modulated to generate optical signal pairs including phase modulated and fixed phase portions, the phase modulated portions having a frequency encoding one or more data symbols and the fixed phase portion having a carrier frequency and a phase corresponding to the immediately preceding phase modulated portion. The output of the laser is passed through an optical spectrum reshaper having a transmission function chosen to attenuate a plurality of the phase modulated portions relative to the fixed phase portions. The phase modulated portions may have N frequency levels located on either side of the carrier frequency. One of the N frequency levels may be equal to the carrier frequency.

Abstract: An optical transmitter is disclosed including a widely tunable laser coupled to a periodic optical spectrum reshaper (OSR) to convert frequency modulated pulses from the laser into amplitude modulated pulses. The laser is tuned to generate pulses corresponding to passbands of the OSR spanning a wide range of frequencies. The laser includes a gain section having an optical path length substantially shorter than the total optical path length of the laser. The laser may be a Y-branch laser having reverse-biased sampled gratings or ring resonator filters tuned by stripe heaters. The laser may also include a reflective external cavity section tunable by modulating the temperature of ring resonators or etalons. The OSR may be integrally formed with the external cavity of the ECL laser.

Abstract: An optical transmitter is disclosed for transmitting a signal along a dispersive medium to a receiver. The optical transmitter generates adiabatically chirped profile having an initial pulse width and frequency excursion chosen such that high frequency data sequences include one bits that interfere destructively at a middle point of an intervening zero bit upon arrival at the receiver.

Abstract: An optical transmitter is disclosed wherein a directly modulated laser outputs a frequency modulated signal through a semiconductor optical amplifier. Both the optical transmitter and semiconductor amplifier are modulated according to an output of a digital data source. An optical filter is positioned to receive an output of the semiconductor optical amplifier and has a frequency dependent transmission function effective to convert the amplified signal into a filtered signal having enhanced amplitude modulation. In some embodiments, the semiconductor optical amplifier is coupled to the digital data source by means of a compensation circuit configured to high-pass filter the output of the digital signal source. In other embodiments, the semiconductor optical amplifier is coupled to the digital data source by means of a compensation circuit configured to produce an output including a first-order time derivative of the output of the digital signal source.

Abstract: A DBR laser, such as a semiconductor DBR laser is disclosed having improved frequency modulation performance. The laser includes a split gain electrode and a tuning electrode. A modulating current encoding a data signal is injected into a first section of the gain electrode whereas a substantially DC bias voltage is imposed on a second section of the gain electrode positioned between the first gain electrode and the tuning electrode. The first and second gain electrodes are electrically isolated from each other and the tuning electrode by a large isolation resistance. In some embodiments, the isolation resistance is generated by forming the electrodes on a P+ layer and removing portions of the P+ layer between adjacent electrodes. Capacitors may couple to one or both of the second gain electrode and the tuning electrode.

Abstract: Thermal chirp compensation in a chirp managed laser. In one example embodiment, a method for thermal chirp compensation in a chirp managed laser (CML) includes several acts. First, a first bias condition and temperature is selected. Next, a first thermal chirp compensation signal is generated. Then, the laser is driven by biasing a first input drive signal with the first thermal chirp compensation signal. Next, a second bias condition and temperature is selected. Then, a second thermal chirp compensation signal is generated. Finally, the laser is driven by biasing a second input drive signal with the second thermal chirp compensation signal.

Abstract: An optical transmitter is discloses having a gain section and a phase section. The phase section is modulated to generate a frequency modulated signal encoding data. The frequency modulated signal is transmitted through an optical spectrum reshaper operable to convert it into a frequency and amplitude modulated signal. In some embodiments, a driving circuit is coupled to the phase and gain sections is configured to simultaneously modulate both the phase and gain sections such that the first signal is both frequency and amplitude modulated.

Abstract: A transmitter includes a frequency modulated laser. An optical spectrum reshaper (OSR) is positioned to receive the frequency modulated signal and has a transmission function effective to convert the frequency modulation to amplitude modulation. An optical fiber channel has a first end positioned to receive the filtered signal and a second end proximate a receiver. A filter is positioned between the second end and the receiver and has a peak transmission frequency thereof located on a transmission edge of the OSR, such as at a peak logarithmic derivative value of the transmission function of the optical spectrum reshaper. In some embodiments a first OSR is positioned to receive the frequency modulated signal and configure to output a filtered signal wherein high frequency portions are more attenuated than low frequency portions. A second OSR at the receiver attenuates the low frequency portions substantially more than the high frequency portions.

Abstract: An optical transmitter comprising: an optical source modulated with an input digital data signal so as to generate a first, frequency-modulated digital signal; and an amplitude modulator, modulated with the logical inverse of the input digital data signal, for receiving the first, frequency-modulated signal and generating a second, amplitude-modulated and frequency-modulated digital signal; wherein the optical source and the amplitude modulator are each configured so as to produce positive transient chirp.

Abstract: This invention discloses a method to control laser dynamics in a gain-switched fiber laser so as to generate stable, clean pulses in an all-fiber format. The gain-switched fiber laser is suitable as a standalone laser source, and as a pump source for harmonic generation and an optical-parametric-oscillator.